E85 is an ethanol fuel blend of 85% denatured ethanol fuel and 15% gasoline or other hydrocarbon by volume. Unfortunately, ethanol is hygroscopic, and as such, bio-fuels like E85 have a greater tendency to succumb to water contamination during engine operation. This water contamination of the fuel can, in some instances, negatively affect the lubrication and detergency of engine oil by introducing free water into the engine compartment. The reduced lubricity and detergency of the engine oil due to the presence of free water in the engine compartment can, in some circumstances, result in premature engine wear. To date, it has been difficult to hinder water from entering into the E85 gasoline during the stages of transport, storage in gas station tanks, and storage in automobile tanks. Accordingly, engine oil formulations often include additives or components to emulsify water in the oil so as to counteract the shortcomings of the water and/or fuel contamination, and therefore usually include an emulsifying agent in the lubricant to do this job.
The emulsifying agent generally should be effective at the emulsification of free water in the oil and remain soluble in the oil over a wide temperature range. Prior emulsifying agents can suffer flocculation and drop out of the oil in some instances and, thus, the effectiveness as an emulsification agent is greatly reduced in these circumstances. Other prior emulsifying agents involve complex chemistries and build multiple components into an emulsifying polymer that tends to drive up manufacturing and component costs with little gain in effectiveness. Other prior emulsifying agents require relatively higher treat rates to achieve desired levels of emulsification, which also drives up costs and formulation complexities.
The effectiveness of the emulsifying agent can be determined using standard tests, such as ASTM D7563-10, the so-called E85 emulsion test. This test evaluates the ability of an engine oil, contaminated with a specified amount of water and simulated E85 fuel, to emulsify the water after agitation, to maintain this emulsion, and to remain substantially free of an aqueous layer at temperatures of 20° C. to 25° C. and −5° C. to 0° C. for at least 24 h. A challenge remains to devise a simple emulsifying agent that can be used in relative low amounts to achieve a stable emulsion over wide temperature ranges.